The present invention relates to a method of regulating the temperature of a coolant in an internal combustion engine which is connected to a radiator by at least one forward and return line and to a coolant pump.
Methods and equipment for cooling the coolant in an internal combustion engine are already known in principle. For example, German Patent No. 37 05 232 describes a method of regulating the temperature of the coolant where a sensor operates a motor actuator as a function of individual engine map characteristics, e.g., rpm and/or engine load, to open or close a bypass valve or the like to achieve a predetermined temperature in the engine coolant circuit. To control the motor actuator, the sensor is heated by a heating device according to the given characteristic data, so it can deliver a suitable signal to the motor actuator. Such a device seems relatively expensive in terms of energy required, because the drive motor for the coolant pump runs constantly, regardless of whether a small amount of waste heat needs to be removed when the internal combustion engine is idling or a large amount when the engine is running.
The method according to the present invention for regulating the temperature of a coolant in an internal combustion engine, however, has the advantage that the speed of the coolant pump is itself regulated or controlled so that its speed corresponds only to the heat to be dissipated.
It is especially advantageous for the speed control to be determined from the temperature difference between the setpoint and the instantaneous temperature of the internal combustion engine, because significant operating states of the engine are detected in this temperature difference.
By preselecting the setpoint temperature as a function of time, the warmup phase of the engine can be controlled easily in an advantageous manner.
It seems especially advantageous to select the setpoint temperature on the basis of a time table, because an especially easy adjustment to different types of engines and their coolant circuits is possible in this way.
The control signal for the coolant pump can be regulated especially easily and advantageously by using a PID controller.
Another advantage is that in addition to controlling the coolant pump, other valves such as the thermostatic valve, the heating valve or an engine fan can also be controlled to optimize the cooling capacity. This additional influence on the coolant circuit can be used either to make the engine warm up more quickly in the cold start phase or to remove excess heat more rapidly at a high load and when the engine is turned off. This reduces exhaust emissions and prevents overheating of the engine.
It also seems advantageous that a suitable display appears when the engine temperature is exceeded, allowing the driver to react appropriately and thus prevent damage.
It is also advantageous that the parameters are linked in stages in the manner of fuzzy logic to guarantee optimal temperature conditions for the internal combustion engine.
By linking the various parameters such as rpm, engine load, vehicle speed and intake temperature or outside temperature, it is possible to form a control signal for the coolant pump which takes into account all the operating conditions that occur.